Conventional phone proxies and call managers may not support more than one device (e.g., Voice over Internet Protocol (VoIP) phone) behind a remote Network Address Translation (NAT) router. Conventional phone proxies may not operate as transparent proxies and also may not see connections from phones to call managers. These limitations may negatively impact the ability to secure and authenticate devices like VoIP phones. However, as devices like VoIP phones become ubiquitous, limitations imposed on VoIP phones accessing call managers will become less and less acceptable.